1. Field of the Invention
The present invention relates generally to an image-pickup apparatus and more particularly to an image-pickup apparatus having a rotatable mirror drive mechanism.
2. Description of the Related Art
A single-lens reflex camera has a quick return mirror mechanism, and can quickly rotate a main mirror and a sub mirror between a position inside an optical path and a position outside the optical path.
At the position inside the optical path, each mirror is positioned at a predetermined stop position by abutting against a mirror down stopper provided in a mirror box, and introduces an incident light from an image-pickup lens to a finder optical system and a focus detection sensor unit. At the position outside the optical path, each mirror evacuates from the optical path by abutting against a mirror up stopper, and an incident light from the image-pickup lens reaches an image-pickup element when a shutter opens.
The quick return mirror mechanism has a spring driving the mirror, a charge mechanism charging the spring by a motor, and a mechanism switching the position inside the optical path and the position outside the optical path, and rotates the mirror by a combination of a link mechanism including the motor, a gear, and the spring.
When the mirror is quickly rotated from the position inside the optical path to the position outside the optical path, up bound phenomenon of the mirror is generated by a collision to the mirror up stopper. A release time lag can be shortened by shorting a time to stop the up bound phenomenon of the mirror, quickly evacuating the mirror outside the optical path for an image-pickup signal from a user, and starting an imaging operation such as a shutter running and an accumulation of the image-pickup element etc.
When the mirror is quickly rotated from the position outside the optical path to the position inside the optical path, down bound phenomenon of the mirror is generated by a collision to the mirror down stopper. The number of taking a picture of continuous shooting per unit time can be increased by shorting a time to stop the down bound phenomenon of the mirror, and early starting a focus operation.
Conventionally, the method of shorting the release time lag by making a spring stronger so as to speed up mirror drive and the method of shorting a mirror charge time by enlarging a motor are proposed to improve by making continuous shooting performance. However, these methods have faults such as the cost is high, the occupation volume is large, and the weight became heavy.
An image-pickup apparatus that drives the mirror by a voice coil motor is proposed in Japanese Patent Laid-Open No. 2010-44271 so as to resolve such a fault.
Moreover, the conventional quick return mirror mechanism had a lot of component counts, and the configuration of the mechanism is complex. In Japanese-Patent Laid-Open No. 11-95317, a mirror mechanism using an actuator of a linear method is proposed as the mechanism which is different from the conventional mechanism in order to displace the mirror quickly and stably, and miniaturize an apparatus.
In the prior art disclosed in Japanese Patent Laid-Open No. 2010-44271, applying an idling current to the voice coil and having a disc brake mechanism are disclosed so that the mirror is held on the position inside the optical path and the position outside the optical path when an electric power is on. Moreover, having a mirror lock mechanism is also disclosed so that the mirror is held on the position outside the optical path when the electric power is off. However, there were faults such as current consumption increases because the drive of the disc brake mechanism and the mirror lock mechanism consume current, cost so as to provide the disc brake mechanism and the mirror lock mechanism is high, and an occupied volume is large.
In the prior art disclosed in Japanese Patent Laid-Open No. 11-95317, the current consumption is remarkable because the actuator of the linear method is need to energize so that the mirror is held on the position inside the optical path and the position outside the optical path mirror. Additionally, the cost is high because the actuator of the linear method needs a lot of expensive magnets.